1. Technical Field
The present invention relates to a multilayer coil component.
2. Description of the Related Art
As the trend toward miniaturization, high-capacity, and high-efficiency of electronic devices such as smart phones, computer tablets, and PCs is accelerating, the importance of electronic components such as inductors constituting them is growing bigger and bigger. The reason is that, as various kinds of electronic devices become smaller and have higher capacitance, electronic components are integrated in a smaller space, electromagnetic interference between electronic components becomes greater, and the number of active elements is increased due to an increase in amount of information to be treated, resulting in an increasing demand for passive elements.
The multilayer coil component including the inductor has been used in many different fields since it has no leakage magnetic flux because of an internal electrode covered with a magnetic material, and suppressed cross-talk; is suitable for high-density assembly and miniaturizable while retaining inductance (L); and maintains high reliability.
This multilayer coil component is usually manufactured by laminating and integrating magnetic sheets or sheets on which a magnetic paste and a paste for internal electrodes are printed by a printing method, a doctor blade method, or the like, and then printing a paste for external electrodes on a surface of a sintered body obtained by firing the laminate at a high temperature and firing it.
As a material for the internal electrode layer, silver (Ag) having low resistivity from the influence of direct current resistance of the multilayer coil component is mainly used. Silver (Ag), which is a noble metal, is not oxidized at a high temperature, and thus, a de-binder process (removing organic substances from a half-finished product at a high temperature) and a sintering process may be employed under a general atmosphere. However, since, in spite of these advantages, silver is a noble metal, it is expensive and temporary price variation thereof is large. Recently, inflated prices of silver impose a heavy burden on product cost, and thus a material as a replacement for silver needs to be developed.
Therefore, many studies on several metals generally useable as an internal electrode instead of silver (Ag) have been conducted. However, since most metals except for copper (Cu) have higher resistivity than silver, they are known to be inappropriate as an internal electrode for general coil elements except for as particular purposes in which low efficiency is ignored.
In order to solve these defects, the action for replacing silver (Ag) with cheap copper (Cu), as a material for the internal electrode of the multilayer coil component, has been made. However, copper has substantially not been used as the material for the internal electrode due to easy oxidation thereof in spite of excellent price competitiveness.
Therefore, in order to replace silver with copper as a material for the internal electrode of the multilayer coil component, the foregoing problems need to be urgently solved,
Meanwhile, a multilayer ceramic condenser (hereinafter, referred to as MLCC) is manufactured by printing a conductive paste on molded dielectric sheets through screen, gravure, or other methods, to thereby form internal electrode layers, and then laminating the sheets having internal electrode layers printed thereon. The internal electrode layers of the MLCC have been known to be formed by using a metal powder mainly such as nickel (Ni), copper (Cu), or the like.
There are many similarities between the MLCC and the multilayer coil component in view of an external shape and a manufacturing method. However, the MLCC is a product where thin square shaped internal electrodes formed on dielectric ceramic sheets are alternately laminated to implement high capacitance, and is a parallel type condenser where the respective internal electrodes are not contacted with each other inside a chip.
Meanwhile, in the case of the multilayer coil component, coil type internal electrodes are formed on a ceramic inner layer and the coil type internal electrodes are connected with each other to implement inductance and impedance of a circuit with respect to current flowing through the coil.
In addition, the MLCC is mainly fired at a high temperature of 1000° C. or higher, and thus has a different mechanism from the multilayer coil component fired at a temperature below 1000° C.
In addition, in the case of the multilayer coil component, the resistance of the internal electrode is increase when the internal electrode is formed of copper, and thus the use of copper is restricted. However, in the case of the MLCC, there is no problem with the resistance (Rdc), and even though the internal electrode is oxidized due to the use of copper as the internal electrode, the application thereof is believed not to be too much trouble.
Therefore, even though copper and nickel are generally used as a material for an internal electrode layer of the existing MLCC, the use thereof as a material for the internal electrode of the multilayer coil component by simple replacement from this technology is still limited.